It is well known to utilize fuel filter assemblies to filter fuel for a combustible engine of a motor vehicle. Such fuel filter assemblies comprise a variety of different orientations of the fuel filter assembly. For example, it is known to utilize sideways, downwardly, and upwardly mounted canisters having a paper filter media enclosed in the canister. With respect to upwardly mounted fuel assemblies, prior art filtration devices have been known to draw fuel into the filter assembly by use of a pump on the outlet side of the filter assembly. The fuel is directed downward into a lower chamber of the filter assembly wherein the fuel flow proceeds upward into an upper filter chamber of the filter assembly. The fuel may then be contained and sealed by a transparent filter cover or closure and a filter mount which may separate the lower chamber from the upper chamber.
Within the filter chamber of the filter assembly, the filter assembly may provide a filter canister comprised of a filter media circling a central filter tube that is contained by filter end caps at the top and bottom of the filter media. The end caps are sealed to the edges of the filter media to preclude any possible leak paths at the ends of the filter canister. The filter media typically comprises a porous paper material that may be pleated or concentrically wound so as to direct the fluid through the filter media. The filter media removes and retains undesirable contaminants within and on the media.
As fluid enters the filter chamber, the fuel level rises and passes through from the outside to the inside of the filter media. The fuel then flows downward into a central passage located along the central axis of the canister. The central passageway is in communication with a fuel outlet wherein the fuel passes outwardly from the filter assembly.
During the filtering process, the fuel is either drawn into the filter chamber by a vacuum or pushed into the filter chamber by pressure until the fuel finds a path through the filter media. As the fuel flows through the filter, dirt and other contaminants larger than the porous openings in the filter media, are trapped and retained by the filter media. These contaminants plug or clog the porous holes in the filter media and restrict or close the paths used by the flowing fuel. The fuel is then forced to seek other open and less restrictive flow openings which are available above the level of the fuel by climbing the height of the filter and accessing the clean areas of the filter media. This process of clogging and climbing continues until the filter media is completely immersed in the flowing fuel.
Even though the filter media may be completely immersed in the flowing fluid, the incoming fuel continues to pass through the filter media. It is not until the filter media becomes greatly clogged that the filter media needs to be replaced. This is a problem since the user generally views the height of the fuel in the filter chamber to see if the filter media is clogged. If the filter media is completely immersed in fuel, the user generally believes that the filter media needs to be replaced. Therefore, this type of system may lead to premature replacement of the filter media.
It would be desirable to provide a fuel filter assembly that provides an accurate indication as to the remaining usefulness of the filter media.